The present invention relates to a flat acoustic converting device, and more particularly to a flat acoustic converting device such as a flat speaker, a flat microphone, a flat speaker which can be used as a microphone, a flat speaker which can be used as an antenna or the like.
FIG. 1 shows the fundamental structure of a conventional flat speaker. The flat speaker comprises a plurality of bar magnets 1 which are arranged in parallel on a yoke 4, a vibrating diaphragm 2 which is provided to be close to and in parallel with the magnetic pole surfaces of the bar magnets 1, and a plurality of coils 3 each of which is formed on the surface of the vibrating diaphragm 2 at a position which corresponds to the magnetic pole surface of each of the bar magnets. A large portion of the internal periphery of each of the coils 3 is situated at a position facing the magnetic pole surface of each of the bar magnets, and the remaining portion of the coil is positioned outside of the position which corresponds to the external edge of the bar magnet. Alternating currents are supplied into the coils 3 in accordance with Fleming""s left-hand rule, and each of the alternating currents is subjected to a force from the magnetic field of each bar magnet. Accordingly, the vibrating diaphragm 2 is vibrated in the direction which is perpendicular to the surface of the vibrating diaphragm 2 so that electric signals can be converted into sound signals.
Further, the vibrating diaphragm 2 is vibrated in the direction which is perpendicular to the surface of the vibrating diaphragm 2 so as to convert sound signals into electrical signals in accordance with Fleming""s right-hand rule. Accordingly, this flat speaker can be used as a microphone.
However, in the above-described conventional flat speaker, because a large portion of the coil is disposed at a position on the surface of the vibrating diaphragm so as to face the magnetic pole surface of each bar magnet, a magnetic field whose orientation is perpendicular to the surface of the vibrating diaphragm acts upon the coil portion which is disposed at a position on the surface of the vibrating diaphragm and which faces the magnetic pole surface of the bar magnet. For this reason, the orientation of the force that an electric current supplied into the aforementioned coil portion receives from the magnetic field is along the surface of the vibrating diaphragm. As a result, problems arise in that the force applied along the surface of the vibrating diaphragm causes twisted portions on the surface of the vibrating diaphragm and thereby forms noise components with respect to the sound signals so that the quality of sound may be deteriorated.
Further, since a plurality of bar magnets are disposed in parallel with each other in the longitudinal directions thereof, the length of each of the bar magnets which link to the magnetic field of each coil is approximately twice as long as the product determined by multiplying the value of the longitudinal side of the bar magnet by the number of windings of the coil. The proportion of the surface area of the vibrating diaphragm occupied by the portion of a coil linking to the magnetic field along the length of the longitudinal side of the bar magnets is low. Therefore, there has been a problem that acoustic conversion efficiency deteriorates so that a sufficient amount of volume and a satisfactory quality of sound cannot be obtained.
Further, the configuration of the speaker is determined by the length of each of the bar magnets and the number of the bar magnets disposed on a vibrating diaphragm, the freedom in designing the configuration of a speaker is limited. Moreover, because a coil is disposed for each of the bar magnets along the longitudinal direction thereof, there arises the problem that there is a lack of flexibility in setting the impedance of a speaker to an appropriate value.
The present invention has been accomplished in order to solve the aforementioned drawbacks of the prior art. It is a first object of the present invention to provide a flat acoustic converting device in which the amount of twisted portions which may form on the vibrating diaphragm is decreased so that noise components can be reduced.
Further, it is a second object of the present invention to provide a flat acoustic converting device in which the length of the portion of the coil linking to the magnetic field is made longer, the proportion of the surface area of the vibrating diaphragm occupied by the portion of the coil is increased to enhance acoustic conversion efficiency and improve the quality of sound.
Further, it is a third object of the present invention to provide a flat acoustic converting device whose configuration can be designed with a high degree of freedom, which can be manufactured simply, and in which the impedance of a speaker can be set with high degree of flexibility.
In order to attain the aforementioned objects, the first object of the present invention is a flat acoustic converting device, comprising: a first magnet in which a first magnetic pole surface of the first magnet is disposed so as to be substantially in parallel with a predetermined face; a second magnet which is disposed so as to be spaced apart from the first magnet at a predetermined distance and so as to be adjacent to the first magnet so that a second magnetic pole surface whose polarity is different from the polarity of the first magnetic pole surface is substantially in parallel with the predetermined face and faces the same side as the first magnetic pole surface of the first magnet; a vibrating diaphragm which is disposed so as to face the predetermined face; a first coil which is formed in a swirled shape, and which is disposed on the vibrating diaphragm at a position where the internal peripheral portion of the swirl is situated at an area adjacent to and including a position corresponding to the external edge of the first magnetic pole surface; and a second coil which is formed in a swirled shape, and which is disposed on the vibrating diaphragm at a position where the internal peripheral portion of the swirl is situated at an area adjacent to and including a position corresponding to the external edge of the second magnetic pole surface.
In accordance with the first aspect of the present invention, the first magnet is disposed so that the first magnetic pole surface having the first polarity (for example, N pole) is provided substantially in parallel with the predetermined face. Further, the second magnet is disposed to be spaced apart from the first magnet and to be adjacent thereto so that the second magnetic pole surface having a second polarity (for example, S pole) which is different from the first polarity is disposed so as to be substantially in parallel with the predetermined face and so as to be directed in the same direction as the first magnetic pole surface of the first magnet. Accordingly, the first magnet and the second magnet are provided so as to be adjacent to each other so that each of the magnetic pole surfaces thereof is provided substantially in parallel with the predetermined face, and the magnetic pole surfaces whose polarities are different from each other are directed in the same direction. Moreover, the first and second magnets can be disposed on the predetermined face. However, the external peripheral portions of the first and second magnets can be supported by a frame body or the like.
A vibrating diaphragm is disposed so as to face the predetermined face. Accordingly, the orientation of the magnetic flux which is generated from each of the magnets is from the first magnetic pole surface to the second magnetic pole surface or from the second magnetic pole surface to the first magnetic pole surface. Accordingly, the orientation of the magnetic flux between the first magnetic pole surface and the second magnetic pole surface, i.e., the orientation of the magnetic flux between the first magnet and the second magnet is substantially in parallel with the surface of the vibrating diaphragm.
The first coil and the second coil, each of which is formed in a swirled shape, are provided on the surface of the vibrating diaphragm. The first coil is disposed on the vibrating diaphragm and corresponds to the first magnet so that the internal periphery of the swirl, i.e., the internal periphery of the coil, is situated on the vibrating diaphragm at the area which includes a position which corresponds to the external edge of the first magnetic pole surface and is adjacent to the position which corresponds to the external edge of the first magnetic pole surface. In the same manner as the first coil, the second coil is disposed on the vibrating diaphragm at a position where the internal peripheral portion of the swirl, i.e., the internal peripheral portion of the coil, is situated in the area adjacent to and including the position corresponding to the external edge of the second magnetic pole surface.
In this way, the first and second coils are disposed on the vibrating diaphragm at a position where the internal periphery of each of the coils is situated in the area adjacent to and including the position corresponding to the external edge of the corresponding magnetic pole surface. Further, as described above, because the orientation of the magnetic flux in the area between the first magnet and the second magnet is substantially in parallel with the surface of the vibrating diaphragm, this magnetic flux whose orientation is substantially in parallel with the surface of the vibrating diaphragm 12 acts upon the portion extending from the internal peripheral portion, which is adjacent to the second coil, to the external peripheral portion of the first coil, and also acts upon the portion extending from the internal peripheral portion of the second coil, which is adjacent to the first coil, to the external peripheral portion of the second coil.
For this reason, when currents are supplied into the first and second coils, the direction of the force received by the current from the magnetic field is substantially perpendicular to the surface of the vibrating diaphragm. Accordingly, because the force along the surface of the vibrating diaphragm decreases, the amount of noise components can be reduced and the sound quality can be improved.
In addition, preferably, the vibrating diaphragm is disposed so as to be adjacent to and facing the first magnetic pole surface and the second magnetic pole surface, because it is possible to increase the amount of the magnetic flux which acts upon the portions of the first coil and the second coil adjacent to each other, and which is directed substantially in parallel with the surface of the vibrating diaphragm. It is possible to situate the first coil and the second coil on the vibrating diaphragm slightly internally of the position at which the internal peripheral portion of each of the coils corresponds to the external edge of the magnetic pole surface. However, it is more effective to situate the first and second coils on the vibrating diaphragm at the position at which the internal peripheral portion corresponds to the external edge of the magnetic pole surface, and more preferably, to situate these coils externally of the position at which the internal peripheral portion corresponds to the external edge of the magnetic pole surface. By disposing each h coil in such a manner as described above, since it is possible to increase the components of the magnetic flux linked to the coil which are directed in parallel with the surface of the vibrating diaphragm, vibrating components, i.e., noise components along the surface of the vibrating diaphragm can be greatly reduced and the sound quality can be improved.
Currents running in the same direction are supplied into the portion of the first coil which is adjacent to the second coil and the portion of the second coil which is adjacent to the first coil. Accordingly, the direction of the force received from the magnetic field by the current running from the internal peripheral portion of the first coil which is adjacent to the second coil through to the outer peripheral portion of the first coil is the same as the direction of the force received from the magnetic field by the current running from the internal peripheral portion of the second coil which is adjacent to the first coil through to the outer peripheral portion of the second coil. As a result, it is possible to generate a sound signal having a large amount of volume.
In order to supply currents into the coils in the same direction, it is possible to separately supply currents into the respective coils. However, as will be described hereinafter, it is possible to supply the currents running in the same direction into the portion of the first coil which is adjacent to the second coil and the portion of the second coil which is adjacent to the first coil by connecting the first coil and the second coil to each other. Namely, in the case in which the winding directions from the external periphery to the internal periphery of the first coil and the second coil are the same, as shown in FIGS. 2A and 2B, the internal peripheral ends of the first coil L1 and the second coil L2 are connected to each other, or alternatively, the external peripheral ends of the first coil L1 and the second coil L2 are connected to each other.
If the winding directions from the external periphery to the internal periphery of the first coil and the second coil are different from each other, as shown in FIGS. 3A and 3B, the internal peripheral end of one of the first coil L1 and the second coil L2 is connected to the external peripheral end of the other of the first coil L1 and the second coil L2. Or as shown in FIG. 3C, the internal peripheral ends of the first coil L1 and the second coil L2 are connected to each other, and the external peripheral ends of the first coil L1 and the second coil L2 are connected to each other. Moreover, the arrows in FIGS. 2 and 3 indicate the directions in which currents are energized.
The second aspect of the present invention is a flat acoustic converting device comprising: a first magnet in which a first magnetic pole surface of the first magnet is disposed so as to be substantially in parallel with a predetermined face; a second magnet which is disposed so as to be spaced apart from the first magnet at a predetermined distance and so as to be adjacent to the first magnet so that a second magnetic pole surface whose polarity is different from the polarity of the first magnetic pole is substantially in parallel with the predetermined face and faces the same side as the first magnetic pole surface of the first magnet; a vibrating diaphragm which is disposed so as to face the predetermined face; a first coil which is formed in a swirled shape, and which is disposed on the vibrating diaphragm at a position where the internal peripheral portion of the swirl is situated at an area adjacent to and including a position corresponding to the external edge of the first magnetic pole surface; a second coil which is formed in a swirled shape winding in the reverse direction of the first coil, and which second coil is disposed on the vibrating diaphragm at a position overlapping the first coil in such a way that the internal peripheral portion of the swirl is situated at an area adjacent to and including a position corresponding to the external edge of the first magnetic pole surface, and the internal peripheral end of the second coil is connected to the internal peripheral end of the first coil; a third coil which is formed in a swirled shape winding in the same direction as the second coil, and which third coil is disposed on the vibrating diaphragm in such a way that the internal peripheral portion of the swirl is situated at an area adjacent to and including a position corresponding to the external edge of the second magnetic pole surface, and the external peripheral end of the third coil is connected to the external peripheral end of the second coil; and a fourth coil which is formed in a swirled shape winding in the same direction as the first coil, and which fourth coil is disposed on the vibrating diaphragm at a position overlapping the third coil in such a way that the internal peripheral portion of the swirl is situated at an area adjacent to and including a position corresponding to the external edge of the second magnetic pole surface, and the internal peripheral end of the fourth coil is connected to the internal peripheral end of the third coil.
Further, since the internal peripheral end of the first coil and the internal peripheral end of the second coil are connected to each other, the internal peripheral end of the third coil and the internal peripheral end of the fourth coil are connected to each other, and the external peripheral ends of the second coil and the third coil are connected to each other, a coil can be formed by a single line which is continuous from the beginning to the end thereof.
In accordance with the second aspect of the present invention, the first coil is disposed on one surface of the vibrating diaphragm, the second coil is disposed on the other surface of the vibrating diaphragm so that the internal peripheral end passes through the vibrating diaphragm so as to be connected to the internal peripheral end of the first coil, and the third coil is disposed on the other surface of the vibrating diaphragm and the fourth coil is disposed on the one surface of the vibrating diaphragm so that the internal peripheral end of the fourth coil passes through the vibrating diaphragm so as to be connected to the internal peripheral end of the third coil. In this way, the vibrating diaphragm can be used effectively by disposing the coils both sides of the vibrating diaphragm.
In accordance with the second aspect of the present invention, the first coil, the second coil, the third coil, and the fourth coil form one set of coil group set. The external peripheral end of the first coil and the external peripheral end of the fourth coil of the coil groups are connected to each other so that a plurality of coil groups can be disposed. Also in this case, because currents in the same direction are flown into coils of the coil groups, which are adjacent to each other and which are disposed on the same surface of the vibrating diaphragm, the conversion efficiency is increased and the occurrence of noise or the like is greatly reduced
The aforementioned coil groups can be stacked in the thickness direction of the coil.
In accordance with the first and second aspects of the present invention, a pair of magnets comprising the first magnet and the second magnet, a pair of coils (in the second aspect of the present invention, from the first coil to the fourth coil) comprising the first coil and the second coil which are provided so as to correspond to the first magnet and the second magnet, respectively, and a vibrating portion of the vibrating diaphragm which corresponds to the area between the first magnet and the second magnet form one unit. Since the vibrating portion operates as an independent vibrating surface, an individual unit can operate as an independent speaker.
As a result, in accordance with the first and second aspects of the present invention, at least one of each of the first magnet and the second magnet is scattered on a predetermined face, namely, are disposed in an irregular order, which is at random, or is in accordance with a predetermined regular order. In this case, as described above, the first and second coils, or the first through fourth coils are situated so as to correspond to each of the first and second magnets which are thus disposed.
In accordance with the first and second aspects of the present invention, a plurality of rows of magnets are positioned in such a way that a row of magnets having the first magnet and the second magnet disposed alternately along a first direction intersects with a second row of magnets having the first magnet and the second magnet disposed alternately along a second direction. By disposing the magnets as described above, a plurality of the first magnets and a plurality of the second magnets can be disposed in the form of a matrix. Further, when the magnets are disposed in the form of a matrix, as described above, the first and second coil or the first to fourth coils are situated on the vibrating diaphragm so that the internal peripheral portion of each of the coils corresponds to each of the first and second magnets which have been disposed.
As described above, by disposing a plurality of the first magnets and a plurality of the second magnets in a state in which they are scattered or in the form of a matrix, a large number of magnets can be disposed as compared to when the bar magnets are disposed in parallel. Because coils equal in number to the number of magnets or to a multiple of the number of magnets can be disposed, the sum of the length of the portions of coils which link to the magnetic flux is made longer, the ratio of the surface of the vibrating diaphragm which is occupied by the coils increases, and the acoustic conversion efficiency is improved so that the sound quality can be improved.
As described above, in the state in which a plurality of the first and second magnets are scattered or in the case in which they are disposed in the form of a matrix, the first coil L1 and the second coil L2 are connected to each other as described in FIGS. 2 and 3. Namely, when the winding directions from the external periphery to the internal periphery of the first and second coils are the same, as shown in FIG. 2A (or FIG. 2B), the internal peripheral ends (or the external peripheral ends) of the first coil L1 and the second coil L2 adjacent to each other are connected to each other, and the external peripheral ends (or the internal peripheral ends) of the first coil L2 and the second coil L1 adjacent to each other are connected to each other. Thus, a plurality of coils are connected to each other.
When the winding directions from the external periphery to the internal periphery of the first and second coils are different from each other and the first and second coils are arranged alternately, as shown in FIG. 3A (or FIG. 3B), the internal peripheral end (or the external peripheral end) of the first coil L1 is connected to the external peripheral end (or the internal peripheral end) of the second coil L2 which is adjacent to the first coil L1. The internal peripheral end (or the external peripheral end) of the second coil L2 is connected to the external peripheral end (or the internal peripheral end) of the first coil L1 adjacent to the second coil L2 and thus a plurality of coils are connected to each other. Moreover, as shown in FIG. 3C, the internal peripheral ends and the external peripheral ends of the first coil L1 and the second coil L2 can be connected to each other.
Further, in the state in which a plurality of the first magnets and a plurality of the second magnets are scattered, or in the case in which they are disposed in the form of a matrix, as shown in FIGS. 2 and 3, a coil group which is formed by the first coil and the second coil which are connected to each other in series is equal to one unit. As shown in FIG. 3C, these coil groups can be connected to each other in parallel.
As described above, the impedance of a flat speaker can be set to an appropriate value by connecting a plurality of coils to each other in series or in parallel or by mixing in-series connections with in-parallel connections. Further, in this way, since coils can be connected freely, it becomes possible to form a coil group with one coil or by connecting a plurality of coils. For this reason, by disposing a plurality of coil groups inside the flat speaker and connecting individual sound sources to each of the coil groups, a multi-channel sound source or a stereophonic source can be provided through a single flat speaker. A single signal source may also be connected to all of the coil groups.
The above-described first and second magnets can be provided on a plate member which is formed from a magnetic material. By disposing the magnets as described above, the area between the first magnet and the second magnet on the plate member can operate as a magnetic path. Because the magnetic flux only passes inside the magnetic path, and does not leak to the outside of the magnetic path, a high density magnetic flux can be generated at the sides of the first and second magnetic pole surfaces so that sound signals having a large amount of volume can be output.
Moreover, when a second plate member which is formed by a magnetic material is disposed on the opposite side of the aforementioned plate member with a vibrating diaphragm interposed therebetween, magnetic flux passes through the inside portion of the second plate member, and can be prevented from leaking to the outside.
At least one of the first magnet and the second magnet can be formed into a plurality of configurations. In this case, the first coil and the second coil can be formed into a winding shape so as to be analogous to the shape of each of the first magnet and the second magnet. By forming these magnets into multiple configurations, it is possible to dispose the first magnet and the second magnet in accordance with the configuration of a flat acoustic converting device. Accordingly, these magnets can be applied to any configuration of the flat acoustic converting device. As a result, it is possible to increase the degree of freedom in designing the whole acoustic converting device.
The above-described magnets and coils can be arbitrarily formed into a triangular, pentagon, hexagon, polygon, circular, elliptical, unfixed shape or the like other than a rectangular shape. Further, as described above, these magnets can be disposed in a state in which they are scattered on a predetermined face or they are disposed in the form of a matrix. For example, coils having a plurality of configurations may be mixed with each other and arranged at random. And as shown in FIG. 4, swirled coils L can be disposed on the surface of the vibrating diaphragm so as to be perpendicular to the magnetic flux whose orientation is along the direction between the respective magnets, and along the surface of the vibrating diaphragm. Accordingly, the entire configuration of an acoustic converting device can be designed freely. And it is possible to form acoustic converting devices having configurations which are different from the devices in the prior art. The setting of impedance can also be carried out more flexibly. Moreover, as shown in FIG. 10, magnets m and coils which are formed into triangular, circular, rectangular, and other pentagon configurations can be disposed in a fixed way.
By the combination of such configurations and layouts of coils and magnets as described above, it is possible to increase the area of the surface of the vibrating diaphragm which is occupied by the coils which wind around the respective magnets by disposing multiple magnets having a small magnetic pole surface, as compared to the case in which a plurality of the bar magnets are disposed in parallel. And it is possible to increase and make uniform the driving force which is driven to the vibrating diaphragm as compared to the case in which the bar magnets are used. For this reason, the conversion efficiency from electrical signals to sound signals thereby increases and the quality of sound can be improved.
In the present invention, the vibrating diaphragm vibrates due to the force that the current which is supplied into coils receives from the magnetic field. However, when the area of the surface of the vibrating diaphragm on which the same coil groups are situated does not vibrate as a whole, a large amount of volume cannot be output, sound may be distorted, or noise may be produced. Therefore, it is necessary to increase the hardness of the area of the vibrating diaphragm on which coils are disposed. On the other hand, the whole of the vibrating diaphragm must vibrate freely in the direction perpendicular to the surface of the vibrating diaphragm. Accordingly, it is necessary to reduce the hardness of the area of the surface of the vibrating diaphragm which surrounds the coil situating area to facilitate the displacement of the coil situating area on the vibrating diaphragm in the direction perpendicular to the surface of the vibrating diaphragm. Therefore, in the present invention, it is preferable to make the hardness of the coil situating area of the vibrating diaphragm on which area the first coil and the second coil are disposed higher than the hardness of the remaining area of the vibrating diaphragm which surrounds the coil situating area. As a result, the hardness of the area of the vibrating diaphragm which supports the coil situating area is reduced, and the vibrating diaphragm can vibrate more effectively.
The structure of the vibrating diaphragm in which a coil situating area whose hardness is made higher than the area which surrounds the coil situating area can be obtained by coating the coil situating area in order to enhance the hardness of the coil situating area, or by fixing the vibrating diaphragm on which coils are situated to another vibrating diaphragm material whose hardness is lower than this vibrating diaphragm.
In accordance with the present invention, as shown in FIGS. 5A and 5B, if magnets m, which are situated adjacent to each other, are disposed so that the polarities thereof are different from each other, because the magnetic flux between the magnets adjacent to each other is oriented from an N pole to two S poles, the magnetic flux of the area between the magnets is directed substantially in parallel with the surface of the vibrating diaphragm. However, even when the polarities of the magnets adjacent to each other are the same, or the polarities of the magnets adjacent to each other are different, as shown in FIG. 6, if the magnetic pole surfaces whose polarities are partially the same are disposed so as to be adjacent to each other, places at which the orientation of the magnet flux reverses are formed at the intermediate portion of each of the N polarities. For this reason, it is necessary to design positions at which the direction in which currents are supplied into coils may reverse with high accuracy, which is not practical. Further, as shown in FIG. 7, if an odd number of triangular magnets m are provided in a circle, a group of magnets whose polarities are the same may be formed adjacent to each other. In this case, the orientation of the magnetic flux between two magnets whose polarities are the same is reversed, ant is therefore not practical. Therefore, as shown in FIGS. 5A and 5B, it is preferable that the magnets adjacent to each other are disposed so as to be positioned in alignment with each other.
The third aspect of the present invention is a flat acoustic converting device, comprising: a magnet which has a first magnetic pole surface on one surface of the magnet and has a second magnetic pole surface whose polarity is different from the polarity of the first magnetic pole surface on the other surface thereof; a first vibrating diaphragm which is disposed so as to correspond to the first magnetic pole surface of the magnet; a second vibrating diaphragm which is disposed so as to correspond to the second magnetic pole surface of the magnet; a first coil which is formed in a swirled shape, and which is disposed on the vibrating diaphragm at a position where the internal peripheral portion of the swirl is situated at an area adjacent to and including a position corresponding to the external edge of the first magnetic pole surface; and a second coil which is formed in a swirled shape, and which is disposed on the vibrating diaphragm at a position where the internal peripheral portion of the swirl is situated at an area adjacent to and including a position corresponding to the external edge of the second magnetic pole surface.
The present invention is structured as one magnet and two vibrating diaphragms and is provided so as to output sound signals from the two vibrating diaphragms at the same time.
As described above, in accordance with the present invention, the first magnet and the second magnet are disposed on a predetermined face so as to be adjacent to each other so that the magnetic pole surfaces thereof whose polarities are different from each other are oriented in the same direction. Accordingly, the orientation of the magnetic flux between the first magnet and the second magnet is substantially in parallel with the surface of the vibrating diaphragm. Further, each of the first and second coils is disposed so that the internal periphery of each coil is situated on the vibrating diaphragm at the area which includes the position which corresponds to the external edge of the magnetic pole surface, and is adjacent to the position which corresponds to the external edge of the magnetic pole surface. Accordingly, the magnetic flux whose orientation is substantially in parallel with the surface of the vibrating diaphragm is linked to both the first coil and the second coil. When a current is supplied into the first coil and the second coil, the direction of the force that the current receives from the magnetic field is substantially perpendicular to the surface of the vibrating diaphragm, and the force which is applied along the direction of the surface of the vibrating diaphragm extraordinarily decreases. As a result, an excellent effect can be obtained in that noise components are reduced and the quality of sound can be improved.
Further, by disposing a plurality of the first magnets and a plurality of the second magnets in a state in which they are scattered or in the form of a matrix, a large number of magnets can be disposed as compared to the case in which the bar magnets are disposed in parallel. Because coils which are equal in number to the number of magnets or a multiple of the number of magnets can be disposed, the sum of the length of the portions of coils which link to the magnetic flux is made longer, the ratio of the surface of the vibrating diaphragm which is occupied by the coils increases, and the acoustic conversion efficiency is improved so that the sound quality can be improved.
The first magnet and the second magnet can be disposed in accordance with the configuration of a flat speaker by forming at least one of the first magnet and the second magnet into multiple configurations. Accordingly, these magnets can be applied to a flat speaker having an arbitrary configuration. As a result, the effect of an increase in the freedom in designing the entire configuration of the flat speaker is obtained.